Effect of inter and intra-row spacing on seed yield and quality of onion (Allium cepa L.) production in Kobo District, Northeastern Ethiopia

Little is known about the optimum plant population for onion seed production and seed quality under irrigated conditions in Ethiopia. To address this gap, an experiment was conducted at Kobo during the 2015 and 2016 irrigation seasons to evaluate the effects of inter-row and intra-row spacing on seed yield and quality of the Bombay Red onion variety. The experiment was arranged in a 4 × 4 factorial combination using a randomized complete block design (RCBD) with three replications. The treatments consisted of four inter-row spacing (0.25, 0.30, 0.35, and 0.40 m) and four intra-row spacing (0.20, 0.25, 0.30, and 0.35 m). Data on growth, seed yield, and quality parameters were analyzed using factorial ANOVA. In terms of seed production, umbel diameter, number of umbels per plant and seeds per umbel were found highly significant ( p < 0.01) between inter-and intra-row spacing. Wider spacing (0.40 m between rows and 0.35 m within rows) produced the maximum number of seeds per umbel (962) and the biggest umbel diameter (6.52 cm). The tallest plants (80.6 cm) were found when the rows were spaced from 0.25 m to 0.20 m from one another. A 0.30 m between rows and 0.20 m between plants had the maximum seed production (1305 kg ha − 1 in 2015 and 1194.2 kg ha − 1 in 2016), mean combined over two years of 1249.6 kg ha − 1 . To optimize seed production, we recommend an inter-row spacing of 0.30 m by an intra-row spacing of 0.20 m for onion seed production in Kobo and comparable agro-ecological locations besides seasonal variability.